The invention relates generally to an insole.
More particularly, the invention relates to an insole which can function as an orthotic.
The foot, which constitutes a bony supporting element for the human skeletal system has an arched structure. This structure is made up of a medial longitudinal arch, a lateral longitudinal arch and a metatarsal arch. Of these, only the lateral longitudinal arch is largely supported by bone. The medial longitudinal arch and metatarsal arch, in contrast, are braced by ligaments and muscles.
The bracing of the arches slackens with increasing age so that the arches fall thereby making the foot longer and wider. This change in foot structure causes the natural padding provided by the sole to be lost and the condition of the foot as a whole deteriorates. Eventually, toe deformations and pressure sores develop.
In an attempt to alleviate these problems, orthotics in the form of insoles have been devised. For instance, the West German Utility Model No. 17 90 894 discloses a shaped insole of foamed material which consists of several superimposed layers and is divided into a small number of large areas having different hardnesses. The lower side of the insole which faces the sole of the shoe or other article of footwear has a different hardness than the upper side which is adjacent to the foot. The hardness of the upper side differs from the hardnesses of the metatarsal pad, the fallen arch support and the heel cushion.
A drawback of conventional orthotic insoles is that these are designed based primarily on static considerations. However, the shape of the foot, as well as its load-carrying ability and efficiency, are influenced not only by static variables but also by dynamic variables.